Succession Flashcards
(16 cards)
What does an ecosystem being dynamic mean?
They are constantly changing
What is succession?
Changes, over time, of the species which occupy a particular area
When does primary succession occur?
Occurs when newly formed/exposed land (with no species present) is gradually colonised by an increasing number of species
What is an example of primary succession?
Glacier retreating, volcanoes erupting -> magma from erupting volcanoes cools
What is a pioneer species?
The first species to colonise the new land
What are some characteristics of pioneer species?
1) asexual reproduction
2) vast quantities of wind dispersed seeds/spores
3) rapid germination of seeds (no period of dormancy)
4) ability to photosynthesise- not dependent on others (bottom of food chain)
5) ability to fix nitrogen from the atmosphere
6) tolerance to extreme conditions
2nd step?
Lichens/moss die and decompose
This releases sufficient nutrients
Organic matter builds up to form a simple soil
Mosses/small ferns begin to grow
These then die and decompose- make conditions less hostile
3rd step?
The topsoil/humus becomes more fertile and enables other species to grow
These plans also die and decompose- leaves organic matter that helps to retain water and provide anchorage for roots
As the small plants/shrubs die and decompose, the new soil becomes deeper and more nutrient rich
The roots of these small plants and shrubs form a network to help the soil in place- prevent from being washed away
3rd step after topsoil/hummus becoming more fertile?
Larger plants and shrubs (small trees also) that require deeper, more nutrient-rich soil can now grow
The soil is sufficiently deep, contains enough nutrients and can hold enough water to support the growth of large trees
The final species to colonise the new land becomes the dominant species
What is the climax community?
The final community formed
What is secondary succession?
From area cleared of organisms, but with soil present e.g. land cleared after a fire
What is a plagioclimax community?
A community which will not develop further as humans are influencing it
E.g. parks
Stops a climax community from developing
What is conservation?
Protecting and managing ecosystems
How can preventing an area from reaching a climax community be a good thing?
Ecosystems at the intermediate stage (small plants) have a distinct diversity of plant species- which may not exist if the climax community was reaches
These diverse plant species also provide food and habitat for a high diversity of animal species- some may be of conservation importance
Why do some conservation projects focus on deliberately preventing succession?
in order to preserve an ecosystem in its current stage of succession
What are some ways of preventing succession?
Grazing animals- can be introduced temporarily- eat the growing shoots of shrubs and trees
Managed burning- the larger woody plants take longer to grow back
